Treatment of crude tar acids for the selective removal of acidic contaminants



. Patented Feb. 6, 1945 I UNITED STATES PATENT TREATMENT OF SELECTIVE I TAMINAN TS CRUDE TAR ACIDS FOR THE REMOVAL OF ACIDIO CON 'Howard G. Cooper and Frederick M. Thatcher,

Clairton, Pa.

No Drawing. Application May 25, 1942,

Serial No. 444,470 1 Claim. (c1. 260-627) operation for the recovery of these tar acids,

such as phenol, cresols, xylenols, etc., the crude tar is distilled and the distillate separated into fractions commonly called light oil, carbolic oil and heavy oil. The carbolic oil fraction contains the tar acids and it is, therefore, treated with caustic soda as the first step in the recovery process. The caustic soda combines with these tar acids, removes them from the oil and puts them into a water solution as sodium phenolate. The sodium phenolate is treated for the removal of entrained oil and the tar acids liberated by neutralization with an acid. The crude tar acids are separated from the water solution and are ready for further processing to recover the various tar acid fractions as phenol, cresol and xylenols.

The separation of these tar acids has been accomplished by treating the crude tar directly with caustic soda, which eliminates the necessity for distilling the tar, and then processing steps, as noted above, for recovery of crude tar acids. This process has been the sub- J'ect of experimentation, and appears to have considerable merit, particularly with regard to processing tar that is not distilled. There is, however, a disadvantage to this process in that a considerable amount of other acidic material fOllOWS the therefore, place the is dissolved in the caustic soda and recovered with the crude tar acids. The amount of undesirable material was found to be 40 to 50% of the crude acids, which compares with 5 to 10% in the acids normally recovered from carbolic oil. .This undesirable material will'remain as a pitch residue on distilling the crude tar acids and its quantity is such that processing for the recovery of phenol, cresols and xylenols cannot be carried out economically.

A study of the cr'ude tar acids recovered from the tar by direct treatment with caustic soda,

has shown the presence of phenol, cresols, xylenols and other acidic materials. It has been found by the inventors of the process described in the following, that the total acidic extract resulting from the direct extraction caustic soda can be processed to remove a major portion of the material which causes the formation of a pitch residue during distillation and,

, residue was removed.

process on an economical basis.

A sample of the acidic extract resulting from.

the direct processing of crude tar with caustic soda was examined and found to contain 34.1% i

of drytar acid distillate and The removal of water.

of water, 40.8% 25.1% of pitch residue. increases this residue to 38.1%, with 5 to 10% of residue in the crude phenols recovered from tar acid oils.

The following is presented. as an example of the procedure that was carried. out for the removal of a substantial amount of the material causing the pitch residue formed during the distillation of acidic material.

One volume of the acidic extract was mixed with two volumes of an organic solvent, such as a mixture of aromatic oils boiling, preferably between 80 and 225 C., which are normally recovered during the distillation of coke oven tar, and heated to approximately 80 C. The oil and extract were found to be miscible at that temperature, but on cooling to normal atmospheric temperature a brown residue settled out which,

was removed by filtration. acids, such as phenol, cresols mained in solution in the oil and were recovered The desirable tar in the normal manner by extraction with caus tic soda. As a result of this work it was found that approximately of the non-volatile pitch The material remaining in the oil solution was removed by extraction with caustic soda, liberated by neutralization of the caustic solution with acid and distilled. It was found tocontain 10.2% of pitch residue, compared with 38.1% of pitch residue in the original material.

We claim:

In the art of separating tar acids from crude tar by treating the latter directly with caustic to produce an acidic extract, the steps of mixing about one volume of said extract with about two volumes of a mixture between and 225 during the distillation of coal tar and which mixture is heated to about 80 C., cooling the resulting mixture and filtering it to remove substantial amounts of material residue during subsequent distillation of said exof tar with 5 tract.

" HOWARD G. COOPER.

- FREDERICK M. 'IHATCHER.

OFFICE which compares and xylenols, re-- of aromatic oils, boiling 0., which are recovered that produce pitch 

